How long does initial therapy usually take before being cleared to start T?

It depends on the doctor. But, if they follow the Harry Benjamin standard, which a lot do, then the person needs either 3 months real life experience living as their desired gender role, or psychotherapy for usually at least 3 months.

Agreed, it's usually 3 months at the very least. However, you CAN go the informed consent route which can shorten (or lengthen) the wait time. I personally went this route, but my doctor followed the WPATH standards of care so it was about a 3 month wait as well.